292 H. SAXTON BURR 
nae were in practical linear continuity. The dorsal laminal were, 
however, sharply interrupted by the di-telencephalic groove. 
The interruption dorsally can be traced to the mechanics of 
evagination. As was indicated above, the long axis of the telen- 
cephalic out-pouching is antero-posterior with the major portion 
of the evagination resulting from the outward swing of the dorsal 
margin. This latter movement results largely from the elabora- 
tion of the dorsal portion of the hemisphere, more particularly 
that portion which is to develop into the primordium hippocampi. 
These factors produce practically no disturbance in the antero- 
posterior continuity of the basal portions of the brain, but in the 
dorso-lateral region of the telencephalon result in what is at first 
a sharp right-angled bend between the dorsal half of the telen- 
cephalon and the corresponding area in the diencephalon. This 
abrupt change in direction of the wall of the neural tube is masked, 
to some extent, later through the dorso-ventral compression of 
the whole brain, though the relative interruption in continuity 
persists. 
We may conclude, therefore, that the cerebral hemisphere in 
Amblystoma is evaginated from relatively undifferentiated alar- 
plate material, which, however, carries with it some evidence 
of the lamination (in the sense of His) of the more caudal portions 
of the neural tube, and that superimposed on this primitive ar- 
rangement is the secondary lamination (in the sense of Herrick) 
which characterizes the cephalic portion of the neural tube in 
older individuals. 
The writer wishes to express his appreciation of the very kind 
and constructive criticism of this paper by Dr. C. J. Herrick, 
without whose generous assistance the work could not have been 
accomplished. 
SUMMARY 
1. The ultimate fate of the ventral boundary of the neuropore 
in Amblystoma larvae is the terminal ridge. 
2. The lamina terminalis produced by the fusion of the lateral 
lips of the neuropore terminates at the terminal ridge. 
